Pretensioner

ABSTRACT

A vehicle safety apparatus has a 3-point seatbelt, with a buckle head, and a crash sensor. A pretensioner is connected at the buckle head of the seatbelt for pulling in a length of seatbelt webbing in response to the crash sensor detecting a crash. The pretensioner has a force reservoir and a piston located within and for movement along a pretensioner cylinder under the force of gas from a gas generator. The piston is connected by a cable to the buckle head of the seatbelt. A cable bracket has an inner and outer guide, and wherein the pretensioner cylinder is attached to the inner guide and the buckle mounting is connected to the outer guide.

FIELD OF THE INVENTION

The present invention relates to a pretensioner for a vehicle occupantsafety restraint and particularly to a buckle pretensioner.

BACKGROUND OF THE INVENTION

Pretensioners are used to rapidly pull in slack in a seatbelt at theonset of a crash to more securely restrain the vehicle occupant againstforward movement and potential injury by collision with the internalstructure of the vehicle. In addition, the pretensioning operation pullsthe occupant into, or at least towards, the correct seating position tomaximize the effect of a second restraint such as an airbag.

A modern seatbelt is known as a 3-point restraint because it is securedto the vehicle at three points arranged about the occupant so as toprovide a diagonal torso section and a horizontal lap portion to holdthe vehicle occupant in the seat. The seatbelt is attached to thevehicle by a spring-loaded retractor tending to pull in the seatbelt,and by a buckle for quick release of the seatbelt.

Pretensioners can be located at the retractor or at the buckle end ofthe seatbelt. The present invention relates particularly to a buckle endpretensioner and aims to provide an improved pretensioner.

SUMMARY OF THE INVENTION

There is provided in accordance with the invention a vehicle safetyapparatus comprising: a 3-point seatbelt having a buckle head, a crashsensor, a pretensioner connected at the buckle head of the seatbelt forpulling in a length of seatbelt webbing in response to the crash sensordetecting a crash, wherein the pretensioner comprises a force reservoircomprising a piston located within and for movement along a pretensionercylinder under the force of gas from a gas generator, the piston beingconnected by a cable to the buckle head of the seatbelt, there being acable bracket having an inner and outer guide, and wherein thepretensioner cylinder is attached to an inner cable guide and the bucklemounting is connected to an outer guide.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how thesame may be carried into effect, reference will now be made, by way ofexample, to the accompanying drawings.

FIG. 1 is an exploded perspective view of the buckle end of a safetyrestraint according to one embodiment of the invention.

FIG. 2 is a cross sectional view of the safety restraint of FIG. 1.

FIG. 3 is an exploded perspective view of the buckle end of a safetyrestraint according to a second embodiment of the invention.

FIG. 4 is an exploded perspective view of the buckle end of a safetyrestraint according to a third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is an exploded view of a first embodiment of the invention. Abuckle head 1, which is arranged to receive a locking tongue from a3-point seatbelt, is attached via a collapsible bellows 2 to an outercable guide that is attached to a load bearing part of the vehicle by alocking bolt 4. A pretensioner 5 is used to rapidly retract to thebuckle head 1 towards the outer cable guide 3 in the event of a crash.The pretensioner comprises a cylinder tube 6 in which slides a piston 7.A cable 8, which in this case is double stranded, connects the piston tothe buckle head 1. Movement of the piston along the cylinder tube pullsthe cable and hence pulls the buckle head down towards its mountingpoint.

The piston 7 is driven along the tube by the force of gas from a gasgenerator 9 located in the cylinder tube 6 within a gas generatorhousing that comprises lower part 10 and upper part 11. Channels 12 areformed by grooves in each of the upper and lower gas generator housings,to accommodate the two strands of a cable 8 as it passes from the pistonand out of the back of the cylinder tube 6.

Of course, any type of known gas generator may be used, including butnot limited to compressed gas cylinders and hybrid inflators in whichgas is generated from chemical reactions.

The two stands of the cable 8 are crimped into a cable assembly 13 thatis secured in the piston 7. An O ring 14 is located in a groove at theforward end of the piston to provide a seal against the internal surfaceof the cylinder 6. The internal surface of the cylinder furthercomprises a series of grooves or saw-tooth formations to engage with areturn motion blocking means 15. This comprises a generally ellipticalplanar member 16 mounted in the piston 7 and biased by a leaf spring 17so that its outer edge engages with the grooves or teeth on the insidesurface of the cylinder. The edge of the elliptical planar member 16,and the shape of the grooves, or teeth, are so profiled that the edge ofthe ellipse moves smoothly past the grooves or teeth on the inside ofcylinder 6 in the pretensioning direction (shown by arrow P), but jamsinto the grooves and blocks a return motion of the piston in theopposite direction. The spring 17 is a leaf spring and the return motionblocking means 15 forms a sub-assembly for ease of manufacture. At theend of the cylinder is a break tube 18 of standard construction, whichslows down the piston at the end of the pretensioning stroke andprevents it emerging from the end of the cylinder (which would of coursebe undesirable and indeed dangerous).

The cylinder 6 is attached to an inner cable guide that has a cast ormolded arcuate channel 20 running through it about a central ring 21.The ring 21 is optionally surrounded by a rotatable roller 22 to reducethe friction felt by the cable 8 as it passes through the channel. Theinner cable guide 19, is surrounded by the outer cable guide 3 and isattached to a low bearing part of the vehicle by a bolt 4 which passesthrough a locking washer 23.

It will be seen that the load from the buckle head 1 is taken by theouter cable guide 3 and the load from the cylinder 6 is taken by theinner cable guide 19, as also is the load from the cable 8. This hasadvantages in strength and in package size. The arrangement of theroller 22 is described in GB 2320469 A published Jun. 24, 1998.

The gas generator assembly 9 is connected by wires 24 to a crash sensor(see FIG. 2) which detects a sudden acceleration or deceleration of thevehicle, or detects an impact, indicative of a crash in this embodimentthese wires are welded to the gas generator assembly to provide a highquality strong joint with a high temperature and shock tolerance.

One of the wires is chosen to be a special product manufactured by thecompany Raychem, which acts as an integral attenuator for the gasgenerator, to prevent accidental firing due to stray electromagneticwaves.

A release indicator 25 is attached to the buckle assembly between thebellows 2 and the outer cable guide 3. A fixing release indicator 26surrounds the release indictor in its mounting position.

FIG. 2 is a cross sectional view of the embodiment of FIG. 1 and likeparts, are denoted by like reference numerals.

A buckle head 1 is connected by bellows 2 and a release indicator fixing26 to the outer cable guide 3 that is secured to the vehicle by a bolt4. The generator sub-assembly 9 is located within gas generator housing12 all of which is contained in cylinder tube 6. A locking ellipse 16together with its biasing spring 17 is located at the rear end of piston7. At the end of the cylinder tube 6 is a break tube 18 to slow thepiston at the end of its stroke.

A crash sensor 27 is connected by a wire 24 to the gas generatorassembly 9. The wire, that preferably includes an attenuator wire,passes through the cable guide 3 into the cylinder 6.

FIG. 3 is a partially cut away and partially exploded view of a secondembodiment of the invention. Again like reference numerals refer likeparts, where appropriate.

A buckle head assembly 1 is connected via a cable 8 and a cable guidebracket 30 to the piston 7. In the vicinity of the buckle head 1, thecable is protected by an outer plastic sleeve 31 that surrounds a washer32 and a damper 33 attached to the cable. The damper 33 is a crush tube,for example an aluminum sleeve with ferrules. This absorbs some of theload at the end of the pretensioning stroke as the buckle is drawntowards the cable bracket 30 and thus reduces the incidence of damage tothe buckle head 1 in a pretensioning operation.

The cable bracket 30 is attached to a fixed part of the vehicle by bolt4 which fits through inner and outer sleeves of a rotating bobbin 34, 35which serves to reduce the friction on the cable as it is pulled backthrough the cable guide 30.

In this embodiment the gas generator 9 is located in a gas generatorhousing 12 which is arranged external of the cylinder tube 6 at an anglethereto. The gas generator housing is formed of a cast or molded partconnected between the cable bracket 30 and the cylinder tube.

The piston is sealed against the inside surface of the cylinder by aseal 36 at one end and an O-ring seal 37 towards the other end.

Return motion of the piston is prevented by a locking ellipse member 16biased by leaf spring 17 located in the piston 7.

FIG. 4 is a partially cut away and partially exploded view of a thirdembodiment of the invention. Again like parts are denoted by likereference numerals where appropriate.

A buckle head 1 is connected by cable 8 to piston 7. The washer 32 and adamper 33, mounted on the cable 8 just below the buckle head, isprotected by a plastic sleeve 31 and further by a bellows 2.

The cable passes through the piston 7 via cable guide bracket 30 whichis covered by an outer bracket trim 40 and fixed to the vehicle by bolt4. Friction between the cable 8 and the guide bracket is reduced usinginner and outer rotating bobbins 34, 35 respectively in the cable guidebracket. A gas generator 9 is located in the externally arranged gasgenerator housing 12.

The piston 7 is sealed in the tube 6 by means of seal 36 and O-ringseals 37. Return motion of the piston is prevented by a locking ellipse16 biased by a leaf spring 17. A use switch connector and cable assemblyis shown at 41. A screw 38 serves to connect the guide bracket 30 to thegas generator housing 12. The cylinder tube 6 may be screwed to fix itinto the gas generator housing 12.

Each of the embodiments described has various features that areinterchangeable with other features of the same embodiment or of theother embodiments. Although several preferred embodiments have beendisclosed and described in detail herein, it should be understood thatthis invention is in now sense limited thereby and its scope is to bedetermined by the appended claims.

What is claimed is:
 1. A vehicle safety apparatus comprising:a 3-pointseatbelt having a buckle head, a crash sensor, a pretensioner connectedat the buckle head of the seatbelt for pulling in a length of seatbeltwebbing in response to the crash sensor detecting a crash, wherein thepretensioner comprises a force reservoir comprising a piston locatedwithin and for movement along a pretensioner cylinder under the force ofgas from a gas generator, said gas generator being electricallyactuatable and electrical connecting wires link the crash sensor to thegas generator and said wires are welded to the gas generator. the pistonbeing connected by a cable to the buckle head of the seatbelt, therebeing a cable bracket having an inner and outer guide, and wherein thepretensioner cylinder is attached to an inner cable guide and the bucklemounting is connected to an outer guide.
 2. The vehicle safety apparatusof claim 1 wherein at least one of said wires is an attenuator toinhibit accidental actuation of the gas generator as a result of strayelectro-magnetic waves.
 3. The vehicle safety apparatus of claim 1further comprising return motion blocking means for preventing movementof the piston in the opposite direction to the pretensioning direction,the blocking means comprising an elliptical planar member mounted to thepiston, having an edge that engages grooves on the inside of thecylinder, the elliptical planar member being inclined to the line ofmovement of the piston and the edge being biased towards the inside wallof the cylinder by a leaf spring, the arrangement being such that theedge rides over the grooves as the piston passes in the pretensioningdirection but so that the edge engages one of the grooves and locks thepiston against further movement in the opposite, return motiondirection.
 4. The vehicle safety apparatus of claim 1 wherein a loadabsorbing crushable tube is arranged around the cable to buckleconnection point and the buckle head to absorb loads generated on thebuckle at the end of a pretensioning stroke.
 5. A vehicle safetyapparatus comprising:a 3-point seatbelt, a crash sensor, a pretensionerconnected at the buckle mounting point of the seatbelt for pulling in alength of seatbelt webbing in response to the crash sensor detecting acrash, wherein the pretensioner comprises a force reservoir comprising apiston located within and for movement along a guide cylinder under theforce of gas from a gas generator, wherein the gas generator iselectrically actuatable and electrical connecting wires link the crashsensor to the gas generator and wherein these wires are welded to thegas generator.
 6. Vehicle safety apparatus comprising:a 3-pointseatbelt, a crash sensor, a pretensioner, connected at the bucklemounting point of the seatbelt, for pulling in a length of seatbeltwebbing in response to the crash sensor detecting a crash, wherein thepretensioner comprises a force reservoir comprising a piston locatedwithin and for movement along a guide cylinder under the force of gasfrom a gas generator, and electrical connecting wires link the crashsensor to the gas generator and wherein at least one of these wires isformed as an attenuator to inhibit accidental actuation of the gasgenerator as a result of stray electro-magnetic waves.
 7. A vehiclesafety apparatus comprising:a 3-point seatbelt, a crash sensor, apretensioner, connected at the buckle mounting point of the seatbelt,for pulling in a length of seatbelt webbing in response to the crashsensor detecting a crash, wherein the pretensioner comprises a forcereservoir comprising a piston located with and for movement along aguide cylinder under the force of gas from a gas generator, and furthercomprising return motion blocking means for preventing movement of thepiston in the opposite direction to the pretensioning direction, theblocking means comprising a locking member mounted to the piston, havingan edge that engages grooves on the inside of the cylinder, the lockingmember being inclined to the line of movement of the piston and the edgebeing biased towards the inside wall of the cylinder by a leaf spring,the arrangement being such that the edge rides over the grooves as thepiston passes in the pretensioning direction but so that the edgeengages one of the grooves and locks the piston against further movementin the opposite, return motion direction.
 8. The vehicle safetyapparatus of claim 7 wherein the grooves preferably have a saw-toothprofile so that the edge contacts the long sides of the teeth in thepretensioning direction and contacts the short sides in the oppositedirection.
 9. The vehicle safety apparatus of claim 8 wherein theblocking member is an elliptically formed, generally planar, piece ofmetal.
 10. The vehicle safety apparatus of claim 7 wherein the blockingmember is an elliptically formed, generally planar, piece of metal.